Conceptual design of Schoenflies motion generators based on the wrench graph

Semaan Amine (1) , Latifah Nurahmi (1) , Philippe Wenger (1) , Stéphane Caro (1)

1 IRCCyN - Institut de Recherche en Communications et en Cybernétique de Nantes

The subject of this paper is about the conceptual design of parallel Schoenflies motion generators based on the wrench graph. By using screw theory and Grassmann geometry, some conditions on both the constraint and the actuation wrench systems are generated for the assembly of limbs of parallel Schoenflies motion generators, i.e., 3T1R parallel manipulators. Those conditions are somehow related to the kinematic singularities of the manipulators. Indeed, the parallel manipulator should not be in a constraint singularity in the starting configuration for a valid architecture, otherwise it cannot perform the required motion pattern. After satisfying the latter condition, the parallel manipulator should not be in an actuation singularity in a general configuration, otherwise the obtained parallel manipulator is permanently singular. Based on the assembly conditions, six types of wrench graphs are identified and correspond to six typical classes of 3T1R parallel manipulators. The geometric properties of these six classes are highlighted. A simplified expression of the superbracket decomposition is obtained for each class, which allows the determination and the comparison of the singularities of 3T1R parallel manipulators at their conceptual design stage. The methodology also provides new architectures of parallel Schoenflies motion generators based on the classification of wrench graphs and on their singularity conditions.

Mots clés: parallel manipulator; conceptual design; Schoenflies motion

Domaines: Automatique / Robotique

Semaan Amine, Latifah Nurahmi, Philippe Wenger, Stéphane Caro. Conceptual design of Schoenflies motion generators based on the wrench graph. ASME 2013 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, Aug 2013, Portland, United States. ⟨10.1115/DETC2013-13084⟩. ⟨hal-00830400⟩